On the relative CNO underabundance in quasar absorption systems at $z \sim 3$ arising from Population III enrichment and attenuation by intermediate-mass black holes and primordial baryon accretion

TL;DR

This study uses an adapted semi-analytical model to explain the low CNO abundance in high-redshift quasar absorption systems by considering Population III stars, black hole sequestration, and primordial baryon accretion.

Contribution

It introduces intermediate-mass black holes as metallicity regulators in cosmic chemical enrichment models, improving agreement with observations.

Findings

IMBHs act as metallicity sinks, reducing CNO overproduction.

The interplay of Pop III yields, CBAR, and IMBH sequestration explains observed abundance patterns.

Black hole processes are crucial in cosmic chemical evolution.

Abstract

This article uses an adapted version of the semi-analytical model of cosmic chemical enrichment developed by \citet{Corazza_2022} to reproduce the observed abundances of C, N, and O in absorption systems of quasar spectra (ASQS) at $z \gtrsim 3-6$, addressing an overproduction issue of the abovementioned elements. We address this discrepancy by updating the cosmic star formation rate (CSFR) and introducing intermediate-mass black holes (IMBHs) as permanent matter sinks without accounting for a dynamic cosmic mass accretion rate. Our results indicate that IMBHs act as essential metallicity attenuators through mass sequestration, providing the physical regulation necessary to reconcile theoretical yields with observed data. We show that the interplay between Pop III yields, the cosmic baryon accretion rate (CBAR) from primordial nucleosynthesis, and mass sequestration by IMBHs mitigates the CNO excess. This work reinforces the role of black hole-driven processes in the chemical evolution of the Universe and identifies IMBH accretion rates as a primary area for future refinement.